I have just bought Wii Sports Resort with Wii Motion Plus and Wii Motion Plus from these guys, Daniel Stores, and the combined price was £31.98. The Wii Sports Resort with accessory was £22.99, and the addition Wii motion plus accessory was £8.99, both of which are the cheapest i've seen anywhere.
To put things into perspective, Game are charging £37,99 for the game (inc. one wii motion plus) and £20 for an additional accessory, combining for £57.99.
I don't know how long the deal will last, but I suggest snapping it up fast.
They have an official warrant from the Queen, so they can be trusted. (Thanks to BargainHunter 69 for pointing that out)